In situ imaging of the interfacial processes manipulated by salt concentration on zinc anodes in zinc metal batteries

Unstable electrode/electrolyte interfaces and heterogeneous Zn deposition would reduce the Coulombic efficiency and cycle life of Zn metal batteries (ZMBs). Applying water-in-salt (WIS) electrolytes has proven to be an effective strategy to address the above issues. However, an understanding of the reaction mechanisms on the Zn anode at nanoscale is still elusive. Here we utilize in situ atomic force microscopy to visualize the solid electrolyte interphase (SEI) formation and Zn deposition/dissolution processes in WIS electrolyte and construct relationships between interfacial behavior and electrochemical performance. The formation processes, chemical properties, and structure of the on-site formed SEI are deeply explored. The SEI with a “plum-pudding” model can guide uniform Zn deposition and reversible dissolution. Mechanistic understanding of the interfacial evolution of the SEI layer and Zn deposition/dissolution has been achieved and will benefit the structural optimization and interfacial engineering of ZMBs.